Many experts now agree that eating a properly balanced snack within twenty to thirty minutes after a hard workout can help speed recovery and increase the amount of muscle gained in each exercise session. Muscles themselves are primarily made of protein, so your shake should include proteins that your body can use as raw materials for repairs and growth. After a workout your body also needs to replenish its stores of energy, so most experts also recommend that your after-workout snack includes some carbohydrates; without these, the proteins cannot be put to good use.

A number of studies have shown that the best snack for after a heavy workout is actually low-fat chocolate milk. It provides the best recovery rate and the most muscle building of all the post-workout drinks studied, and it has the bonus of being both safer for you and much less expensive than the commercial protein shakes. (You should also know that many of the brands of protein powder and protein shake have been found to have high levels of heavy metals, which can harm your body.)